Nutrient-dependent Secretion of Glucose-Dependent Insulinotropic Polypeptide From Primary Murine K Cells

Diabetologia. 2009 Feb;52(2):289-298. doi: 10.1007/s00125-008-1202-x. Epub 2008 Dec 11.

Abstract

Aims/hypothesis: Glucose-dependent insulinotropic polypeptide (GIP) is an incretin hormone with anti-apoptotic effects on the pancreatic beta cell. The aim of this study was to generate transgenic mice with fluorescently labelled GIP-secreting K cells and to use these to investigate pathways by which K cells detect nutrients.

Methods: Transgenic mice were generated in which the GIP promoter drives the expression of the yellow fluorescent protein Venus. Fluorescent cells were purified by flow cytometry and analysed by quantitative RT-PCR. GIP secretion was assayed in primary cultures of small intestine.

Results: Expression of Venus in transgenic mice was restricted to K cells, as assessed by immunofluorescence and measurements of the Gip mRNA and GIP protein contents of purified cells. K cells expressed high levels of mRNA for Kir6.2 (also known as Kcnj11), Sur1 (also known as Abcc8), Sglt1 (also known as Slc5a1), and of the G-protein-coupled lipid receptors Gpr40 (also known as Ffar1), Gpr119 and Gpr120. In primary cultures, GIP release was stimulated by glucose, glutamine and linoleic acid, and potentiated by forskolin plus 3-isobutyl-1-methylxanthine (IBMX), but was unaffected by the artificial sweetener sucralose. Secretion was half-maximal at 0.6 mmol/l glucose and partially mimicked by alpha-methylglucopyranoside, suggesting the involvement of SGLT1. Tolbutamide triggered secretion under basal conditions, whereas diazoxide suppressed responses in forskolin/IBMX.

Conclusions/interpretation: These transgenic mice and primary culture techniques provide novel opportunities to interrogate the mechanisms of GIP secretion. Glucose-triggered GIP secretion was SGLT1-dependent and modulated by K(ATP) channel activity but not determined by sweet taste receptors. Synergistic stimulation by elevated cAMP and glucose suggests that targeting appropriate G-protein-coupled receptors may provide opportunities to modulate GIP release in vivo.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / genetics
  • Animals
  • Calcium-Binding Proteins / genetics
  • Chromosomes, Artificial, Bacterial
  • Cyclic AMP / metabolism
  • Flow Cytometry
  • Gastric Inhibitory Polypeptide / genetics
  • Gastric Inhibitory Polypeptide / metabolism
  • Glucose / pharmacology*
  • Killer Cells, Natural / cytology
  • Killer Cells, Natural / drug effects
  • Killer Cells, Natural / metabolism*
  • Lipoproteins / genetics
  • Mice
  • Mice, Transgenic
  • Promoter Regions, Genetic
  • Rats
  • Receptors, Gastrointestinal Hormone / physiology
  • Tetradecanoylphorbol Acetate / pharmacology

Substances

  • Actins
  • Calcium-Binding Proteins
  • Lipoproteins
  • Receptors, Gastrointestinal Hormone
  • calcium binding protein p22, rat
  • Gastric Inhibitory Polypeptide
  • gastric inhibitory polypeptide receptor
  • Cyclic AMP
  • Glucose
  • Tetradecanoylphorbol Acetate